How to tell from within a renderer process that it has tabs?

[Simon Que]

How can my code in the Chrome renderer process know that it is running in a renderer process that includes one or more tabs? As opposed to in a renderer process containing extensions or plugins.

Simon

[PhistucK]

Renderers with normal web pages generally have --type=renderer in their command line.

https://code.google.com/p/chromium/codesearch#chromium/src/content/common/sandbox_win.cc&q=%22switches::kRenderer%22&sq=package:chromium&type=cs&l=672

https://code.google.com/p/chromium/codesearch#chromium/src/content/common/sandbox_win.cc&q=%22switches::kRenderer%22&sq=package:chromium&type=cs&l=727

However, I recall instances where renderers were unfortunately shared by extensions and normal web pages, so if a complete distinction is important to you, I am not sure there is one.

☆PhistucK

On Wed, Mar 30, 2016 at 8:31 AM, Simon Que <sq...@chromium.org> wrote:

How can my code in the Chrome renderer process know that it is running in a renderer process that includes one or more tabs? As opposed to in a renderer process containing extensions or plugins.

Simon

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[Simon Que]

Yes I know... I was asking specifically how to identify a renderer process as having tabs, assuming I already know it is a renderer process.

[Avi Drissman]

You can't.

From the perspective of the content layer, a WebContents is a WebContents, and it doesn't know or care about what is in it.

A WebContents might be used in a tab, or in an extension, or heck, used in Opera or Chromecast. There is no way to know, and any code that needs to know can't be put into that layer.

Avi

[Colin Blundell]

FWIW, the original email said the *Chrome* renderer process, which makes me assume that it would be fine to use any //chrome-specific information available to answer this question.

[Avi Drissman]

Simon, what exactly are you trying to do? As PhistucK pointed out, the render process might be shared. Do you want to know if a specific frame is in a tab? (You could attach a tab helper and have that send IPCs to your code in the render process, etc.) Why were you asking about the entire process?

Avi

[Simon Que]

I have some code that I'd like to profile for performance. It can run in any process, and eventually it will be randomized to run in only e.g. 1 in 10 processes. But I can't profile that directly because it is non-deterministic.

Instead, I'd like to have only 1 tab open, and the code running in the process that contains that tab. The test code would only run if it is in a renderer process (determined by looking at cmdline flags) that contains a tab (what I'm asking about).

[Will Harris]

Extension processes have --extension-process on them. Renderer processes can't contain plugins, so any Chrome process with --type=renderer without --extension-process should be a renderer displaying tab content. It might contain multiple tabs though.

It might be best to mediate this via the browser though, since the browser has the definitive knowledge of what every child process is doing and what it's hosting.

Will

[Matt Falkenhagen]

One exception is a renderer created for a service worker that is not shared with a page. It would not display tab content yet would have --type=renderer.

[Avi Drissman]

Is this test code, or code we'll be shipping?

Your code would need to live in the browser, on the chrome side of content (obviously as it deals with tabs) and would need to coordinate what lives on the renderer side.

[Simon Que]

This is just test code.